On 2/14/19 7:23 AM, Tom Tromey wrote: >>>>>> "Marc" == Marc Glisse <marc.gli...@inria.fr> writes: > >>> Lastly, in the case of uninitialized variables, the usual solution >>> of initializing them is trivial and always safe (some coding styles >>> even require it). > > Marc> Here it shows that we don't work with the same type of code at all. If > Marc> I am using a boost::optional, i.e. a class with a buffer and a boolean > Marc> that says if the buffer is initialized, how do I initialize the > Marc> (private) buffer? Or should boost itself zero out the buffer whenever > Marc> the boolean is set to false? > > This is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635 (I know you > know, but maybe others on the thread don't). > > I think in this specific case (std::optional and similar classes), GCC > should provide a way for the class to indicate that > -Wmaybe-uninitialized should not apply to the payload. > >>> A shared definition of a false positive should be one of the very >>> first steps to coming closer to a consensus. Real world (as opposed >>> to anecdotal) data on the rates of actual rates of false positives >>> and negatives vs true positives would be also most helpful, as would >>> some consensus of the severity of the bugs the true positives >>> expose, as well as some objective measure of the ease of >>> suppression. There probably are others but these would be a start. > > Marc> This data is going to be super hard to get. Most projects have been > Marc> compiling for years and tweaking their code to avoid some warnings. We > Marc> do not get to see the code that people originally write, we can only > Marc> see what they commit. > > gdb has gone through this over the years -- it turns on many warnings > and sometimes false positives show up. Most of the time there's a > comment, for -Wmaybe-uninitialized grep for "init.*gcc" in the source. > Unfortunately the comment isn't standardized; but I only get ~20 hits > for this in gdb, so it isn't really so bad in practice. Yea, in retrospect we should have had a consistent marker for GCC as well. I suspect a goodly number of those initializations that went in early in the process are no longer needed.
Jeff
